astroengine writes: The High-Resolution Imaging Science Experiment (HiRISE) camera carried by NASA's Mars Reconnaissance Orbiter (MRO) has spotted a strange geological feature that, for now, defies an obvious explanation. Found at the southern edge of Acidalia Planitia, small pits with raised edges appear to hug a long ridge. So far, mission scientists have ruled out impact craters and wind as formation processes, but have pegged the most likely cause to be glacial in nature.Link to Original Source